Oda here!
I post little-known facts about electric guitars on X (Twitter), but
Since X has character limits, I'll share more detailed trivia here in this update!
Knowing this won't make you a better guitarist or anything, but I'd be happy if you just think "Huh, interesting."
(Though, knowing more about guitars = liking them more = practicing more = maybe getting better? lol)
I'm writing this while thinking "Huh!" myself, so let's say "Huh!" together!!
Part 3 covered body wood/finish/neck plate/pickguard/knobs.
This time it's the tremolo unit/patent number edition.
We summarized the tremolo units—the Stratocaster's defining feature—by era,
and traced the evolution of patent numbers on the headstock using photos of past arrivals from TC Instruments' 35-year history!
This time, we have an announcement for everyone who's been saying "Huh~" with us!
We'd be thrilled if you read to the end♪
Bridge
1950s-1960s
The Synchronized Tremolo Unit, the defining feature of the Fender Stratocaster.
From its birth in 1954 through the 1960s, there were minor changes like chamfered screw holes, block hole dimensions, and set screw length, but no major alterations!
The block was made of iron. Saddles were formed by pressing iron plates.
The bridge, arguably the heart of the sound
.
It's fair to say that the part defining the Stratocaster as a Stratocaster was essentially perfected from the very beginning!
1970s
Starting in 1972, the inertia block changed from a separate steel type to an integrated design with a zinc die-cast bridge plate and block. Simultaneously, the saddles also switched to die-cast construction, resulting in a significant change in the sound character.
Two-Point Support Tremolo Unit
The traditional tremolo units introduced so far use a " six-point support " system, attached to the body with six screws, and remain the standard today.
However, in recent years, models adopting a " two-point support " system have also appeared!
The biggest advantage is the wider range of motion for the arm!
Since the tension load on each string is applied at only two points, it's also said to offer slightly higher tuning stability.
The photo shows the Jeff Beck model!
Tremolo Arm
The Stratocaster tremolo arm underwent two specification changes between 1954 and 1983.
From 1954 to around 1964, it was chrome-plated steel. From 1964 to early 1982, it was stainless steel without plating. From 1982 to 1983, it reverted to chrome-plated steel.
Models up to 1957 are characterized by a larger angle at the tip.
From the 60s onward, the bend becomes smaller, with many arms being nearly straight.
Even among current Fender genuine replacement parts, the Vintage Series offers both 50s and 60s arms. It's just an angle, but it's an angle—preferences really do vary quite a bit. 👀
Patent Number
Patent Number refers to
1954~ Spaghetti Logo
No patent number listed 
1961~ Spaghetti Logo
2.573.254 Telecaster Bridge and Pickup Assembly
2.741.146 Synchronized Tremolo 
1962~ Spaghetti Logo
2.573.254 Telecaster Bridge and Pickup Assembly
2.741.146 Synchronized Tremolo
2.960.900 Contour Body 
Late 1964~ Transition Logo
2.573.254 Telecaster Bridge and Pickup Assembly
2.741.146 Synchronized Tremolo
2.960.900 Contour Body
3.143.028 Adjustable Neck 
Mid-1965~ Transition Logo
2.573.254 Telecaster Bridge and Pickup Assembly
2.741.146 Synchronized Tremolo
2.960.900 Contour Body
3.143.028 Adjustable Neck
2.817.261 Hum-Canceling Pickup
(This is a patent for humbucker pickups used on lap steel guitars
.
Filed 3/29/1956)
Unfortunately, I couldn't find a photo for this.
1966~ Transition Logo
2.741.146 Synchronized Tremolo
3.143.028 Adjustable Neck
DES 169062 PrecisionBass Shape 
Late 1968~ CBS Logo
2.741.146 Synchronized Tremolo
3.143.028 Adjustable Neck 
Early 1971~ CBS Logo "WITH SYNCHRONIZED TREMOLO" marking disappears
2.741.146 Synchronized Tremolo
Late 1971~ CBS Logo
3.143.028 Adjustable Neck 
1976~ CBS Logo
Patent numbers are no longer listed; instead, the serial number and "Made in USA" appear below the logo. 
What did you think!
Thank you for watching until the end this time as well.
Now, as mentioned at the beginning, we have an announcement!
The "Learn with Oda♪ Fender Trivia" series, which we've released over four episodes,
has now been compiled into a complete collection covering Episodes 1-4!!
It's quite long since it's a complete collection! (lol)
We've re-shot all the photos and organized it for better readability, so we'd be thrilled if you could take a look!
Oda's Fender Trivia♪ Episodes 1-4 Compilation
I also post daily on X (formerly Twitter), so please follow me there too!
Oda